What are the recommended antibiotics for treating urinary tract infections (UTIs)?

Recommended Antibiotics for Urinary Tract Infections

For uncomplicated UTIs in women, use nitrofurantoin, trimethoprim-sulfamethoxazole (TMP-SMX), or fosfomycin as first-line therapy, with treatment duration generally no longer than 7 days. 1

First-Line Antibiotic Selection for Uncomplicated Cystitis

The choice of first-line agent must be guided by your local antibiogram, as resistance patterns vary significantly by region. 1

The three recommended first-line agents are:

• Nitrofurantoin - preferred when local resistance is acceptable 1
• Trimethoprim-sulfamethoxazole (TMP-SMX) - use only if local resistance <20% 1
• Fosfomycin - single 3g dose option 1, 2

These agents are prioritized because they effectively treat UTIs while causing less "collateral damage" (disruption of normal flora and selection for resistance) compared to fluoroquinolones and broad-spectrum beta-lactams. 1

Treatment Duration

Treat for as short a duration as reasonable, generally no longer than 7 days. 1 The 2019 AUA/CUA/SUFU guidelines emphasize antibiotic stewardship by limiting treatment duration to balance symptom resolution against resistance risk. 1

Specific durations by agent:

• Nitrofurantoin: 5 days 2, 3
• TMP-SMX: 3 days 2
• Fosfomycin: single 3g dose 2, 3

Single-dose antibiotics show increased bacteriological persistence compared to 3-6 day courses, so avoid single-dose regimens except for fosfomycin. 1

Second-Line Options

When first-line agents cannot be used due to resistance patterns or allergies, consider:

• Fluoroquinolones (ciprofloxacin, levofloxacin) - only if local resistance <10% 1
• Oral cephalosporins (cephalexin, cefixime) 2
• Beta-lactams (amoxicillin-clavulanate) 2

Critical caveat: Avoid fluoroquinolones for empiric treatment if the patient has used them in the last 6 months or is from a urology department where resistance rates are typically higher. 1

Uncomplicated Pyelonephritis

For outpatient oral therapy of uncomplicated pyelonephritis, the 2024 European Association of Urology guidelines recommend: 1

Oral regimens:

• Ciprofloxacin 500-750 mg twice daily for 7 days (if fluoroquinolone resistance <10%) 1
• Levofloxacin 750 mg daily for 5 days 1
• TMP-SMX 160/800 mg twice daily for 14 days 1
• Cefpodoxime 200 mg twice daily for 10 days 1

Important: Nitrofurantoin, fosfomycin, and pivmecillinam should be avoided for pyelonephritis as there are insufficient data regarding their efficacy for upper tract infections. 1

For hospitalized patients requiring IV therapy, use fluoroquinolones, aminoglycosides (with or without ampicillin), or extended-spectrum cephalosporins/penicillins. 1

Complicated UTIs

For complicated UTIs with systemic symptoms, use combination therapy: 1

• Amoxicillin plus an aminoglycoside, OR
• Second-generation cephalosporin plus an aminoglycoside, OR
• IV third-generation cephalosporin

Treatment duration is 7-14 days (14 days for men when prostatitis cannot be excluded). 1

Essential principle: Always manage the underlying urological abnormality or complicating factor—antibiotics alone are insufficient. 1

Multidrug-Resistant Organisms

For ESBL-producing Enterobacterales:

Oral options for cystitis:

• Nitrofurantoin 2
• Fosfomycin 2, 4
• Pivmecillinam 2

Parenteral options for complicated infections:

• Ceftazidime-avibactam 2.5g IV every 8 hours 1
• Meropenem-vaborbactam 4g IV every 8 hours 1
• Imipenem-cilastatin-relebactam 1.25g IV every 6 hours 1

For carbapenem-resistant Enterobacterales (CRE):

Treatment duration 5-7 days for UTI: 1

• Ceftazidime-avibactam 2.5g IV every 8 hours 1
• Meropenem-vaborbactam 4g IV every 8 hours 1
• Aminoglycosides (gentamicin 5-7 mg/kg/day or amikacin 15 mg/kg/day) for UTI only 1

Critical Pitfalls to Avoid

Do not treat asymptomatic bacteriuria except in pregnant women or patients scheduled for invasive urinary procedures. 1 Treatment of asymptomatic bacteriuria in other populations, including diabetics and long-term care residents, provides no benefit. 1

Obtain urine culture before treatment in patients with recurrent UTIs to guide therapy based on susceptibility patterns. 1 This allows tailoring of therapy and helps distinguish true UTI from alternative diagnoses. 1

Avoid empiric fluoroquinolones in areas with high resistance rates (>10%) or in patients recently exposed to them, as this drives further resistance. 1

For catheter-associated UTIs, treat according to complicated UTI recommendations and always obtain urine culture before initiating therapy. 1 The mortality associated with catheter-associated bacteremia is approximately 10%. 1

FDA-Approved Dosing for TMP-SMX

For uncomplicated UTIs, the FDA-approved dosing is 1 double-strength tablet (160mg TMP/800mg SMX) every 12 hours for 10-14 days, though shorter courses (3 days) are now preferred based on guideline recommendations. 5